In integrated circuit packaging processes, a die may be bonded onto a package substrate using flip-chip bonding, wherein solder bumps are used to join the bond pads on the die to the bond pads on the package substrate. After the solder bumps are reflowed, an underfill is disposed into the gap between the die and the package substrate. The underfill is then cured, and the solder bumps are protected by the underfill.
In conventional flip-chip packaging, the underfill is filled into the gap between the die and the package substrate through capillary underfill dispensing. As a result, depending on the viscosity of the underfill, although some of the underfill may climb on the sidewalls of the die, the underfill is typically limited to be on the lower parts of the sidewalls of the die, if it ever climbs on the sidewalls of the die. It is less likely that the underfill may climb on the upper parts of the sidewalls of the die. Situation also occurs that the underfill may not climb on any portion of the sidewalls of the die at all. Lacking underfill at the corners of the die causes an increase in the risk of the delamination between different layers in the die and the delamination between the die and the underfill.